To Scarlett, Carreen is still the baby, and is too young to act mature. She also thinks this about Carreen and Brent. Scarlett never knows how much Carreen loves Brent.
"To Scarlett, Carreen was still baby, and was too young to fall in love."
But Scarlett is more okay with Carreen than the hateful, lazy, and snobbish Suellen.
Carreen: (To Suellen) "Don't worry. I'll pick cotton for both of us!"
Scarlett: "Thank you, sugarbaby."